Polyurethane derived from castor oil monoacylglyceride (Ricinus communis) for bone defects reconstruction: characterization and in vivo testing

Abstract

Biomaterials used in tissue regeneration processes represent a promising option for the versatility of its physical and chemical characteristics, allowing for assisting or speeding up the repair process stages. This research has characterized a polyurethane produced from castor oil monoacylglyceride (Ricinus communis L) and tested its effect on reconstructing bone defects in rat calvaria, comparing it with commercial castor oil polyurethane. The characterizations of the synthesized polyurethane have been performed by spectroscopy in the infrared region with Fourier transform (FTIR); thermogravimetric analysis (TG/DTG); X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). For the in vivo test, 24 animals have been used, divided into 3 groups: untreated group (UG); control group treated with Poliquil® castor polyurethane (PCP) and another group treated with castor polyurethane from the Federal University of Piauí - UFPI (CPU). Sixteen weeks after surgery, samples of the defects were collected for histological and histomorphometric analysis. FTIR analysis has shown the formation of monoacylglyceride and polyurethane. TG and DTG have indicated thermal stability of around 125 °C. XRD has determined the semi-crystallinity of the material. The polyurethane SEM has shown a smooth morphology with areas of recesses. Histological and histomorphometric analyzes have indicated that neither CPU nor PCP induced a significant inflammatory process, and CPU has shown, statistically, better performance in bone formation. The data obtained shows that CPU can be used in the future for bone reconstruction in the medical field.

Fig. 1

FTIR spectra: a castor oil, b glycerol, c MAG; d HDI and e CPU

Fig. 2

a TG and DTG curves for CPU polyurethane; b Diffractogram of polyurethane with crystallinity peak around 195.2 °C

Fig. 3

SEM images of castor/UFPI polyurethane sample; a flat, regular and continuous surface, with no pores (2000×); b homogeneous surface with protrusions and depressions, fracture and artifacts (500×)

Fig. 4

Photomicrographs of bone repair in a critical rat calvaria defect, after 16 weeks, in UG group (a, a1, and a2), PCP group (b, b1, and b2), and CPU group (c, c1, and c2). FC fibrous capsule, FCT fibrous connective tissue, LCT loose connective tissue, NB newly formed bone, OM osteoid matrix, PEB pre-existing bone; *polyurethane particle. H.E. Hematoxylin-Eosin, MT Masson’s trichrome. Scale bar: 2 and 10 µm